Charge-coupled amplifier

Abstract

A charge-coupled amplifier having a transistor used for transferring an electric charge between capacitors is provided with a charging means for charging the capacitor connected to an emitter of the transistor at a level of a sample-held signal voltage, and a differential signal voltage between the sample-held signal voltage and another sample-held signal voltage applied to a base is derived from a collector of the transistor with a delay of one sampling interval. So that, the charge-coupled amplifier has faculties of a differential amplifier and an analog shift register. Accordingly, a serial-parallel type A-D converting device having a high exactness can be formed simply by using the charge-coupled amplifier.

What is claimed is: 
     
       1. A charge-coupled amplifier comprising: a first transistor having first, second and third electrodes,   a first capacitor having one end connected at a first connecting point to the first electrode of said first transistor, a first pulse voltage being applied to the other end of said first capacitor,   a second capacitor having one end connected at a second connecting point to the second electrode of said first transistor and the other end being maintained at a reference potential,   a first directional device having one terminal connected to said first connecting point, a second pulse voltage being applied to a second terminal of said first directional device for charging said first capacitor,   a sample-holder,   a second directional device coupled between said first connecting point and the output of said sample-holder for sampling and holding a first input signal applied to said sample-holder in response to a third pulse voltage, said second directional device providing a path for charging said first capacitor so that the voltage across said first capacitor is maintained at a level corresponding to that of said first input signal,   a third directional device having one terminal coupled to said second connecting point, a fourth pulse voltage being applied to a second terminal of said third directional device for charging said second capacitor so that the voltage across said second capacitor is maintained at a constant level, and,   means for applying a second input signal to the third electrode of said first transistor, whereby an electric charge corresponding to the level difference between said first and second input signals is transferred periodically through said first transistor from said second capacitor to said first capacitor in response to said first, second, third and fourth pulse voltages so that an output signal corresponding to said level difference between said first and second input signals appears at said second connecting point.   
     
     
       2. A charge-coupled amplifier as defined by claim 1 wherein the first, second and third electrodes of said first transistor correspond to the emitter, collector and base thereof respectively, said first directional device comprises a second transistor having a collector connected to said first connecting point and a diode connected between the base and emitter of said second transistor, and said third directional device is a diode. 
     
     
       3. A charge-coupled amplifier as defined by claim 1 wherein said first directional device is a diode. 
     
     
       4. A charge-coupled amplifier as defined by claim 1 wherein said third directional device comprises a third transistor having a collector connected to said second connecting point and a diode connected between the base and emitter of said third transistor. 
     
     
       5. A charge-coupled amplifier as defined by claim 4 which further comprises a diode having its anode connected to said second connecting point, a fourth transistor having a collector connected to a d.c. voltage source and an emitter connected to the cathode of said diode, and a load resistor coupled to the junction of said diode and the emitter of said fourth transistor. 
     
     
       6. A charge-coupled amplifier as defined by claim 1 wherein said second directional device is a diode. 
     
     
       7. A charge-coupled amplifier as defined by claim 1 wherein said second directional device comprises a fifth transistor having a collector coupled to said first connecting point and an emitter coupled to the output of said sample holder, and a differential amplifier having first and second inputs connected to the emitter and collector of said fifth transistor respectively and an output coupled to the base of said fifth transistor. 
     
     
       8. In combination with a charge-coupled amplifier, an analog to digital converting device comprising: a sample-holder for storing an input analog signal coupled to the input of said charge-coupled amplifier,   a first analog-to-digital converter coupled to the junction between the output of said sample-holder and the input of said charge-coupled amplifier, said first analog-to-digital converter converting the analog signal at the output of said sample-holder to upper bits of a digital signal,   a digital-to-analog converter coupled to the output of said first analog-to-digital converter and to said charge-coupled amplifier for converting said upper bits to an analog signal and coupling said analog signal to said charge-coupled amplifier, said amplifier delaying the analog signal from the sample-holder and acting as a differential amplifier, and   a second analog-to-digital converter coupled to the output of said charge-coupled amplifier, said second analog-to-digital converter converting the differential output analog signal at the output of said charge-coupled amplifier to lower bits of said digital signal.